Data of our compiled catalog containing the positions, velocities, and metallicities of 415 RR Lyrae variable stars and the relative abundances [el/Fe] of 12 elements for 101 RR Lyrae stars, including four α elements (Mg, Ca, Si, and Ti), are used to study the relationships between the chemical and spatial-kinematic properties of these stars. In general, the dependences of the relative abundances of α elements on metallicity and velocity for the RR Lyrae stars are approximately the same as those for field dwarfs. Despite the usual claim that these stars are old, among them are representatives of the thin disk, which is the youngest subsystem of the Galaxy. Attention is called to the problem of low-metallicity RR Lyrae stars. Most RR Lyrae stars that have the kinematic properties of thick disk stars have metallicities [Fe/H] < −1.0 and high ratios [α/Fe]≈ 0.4, whereas only about 10 % of field dwarfs belonging to the so-called "lowmetallicity tail" have this chemical composition. At the same time, there is a sharp change in [α/Fe] in RR Lyrae stars belonging just to the thick disk, providing evidence for a long period of formation of this subsystem. The chemical compositions of SDSS J1707+58, V455 Oph, MACHO 176.18833.411, V456 Ser, and BPS CS 30339-046 do not correspond to their kinematics. While the first three of these stars belong to the halo, according to their kinematics, the last two belong to the thick disk. It is proposed that they are all most likely extragalactic, but the possible appearance of some of them in the solar neighborhood as a result of the gravitational action of the bar on field stars cannot be ruled out.

Based on our compiled catalogue of fundamental astrophysical parameters for 593 open clusters, we analyze the relations between the chemical composition, spatial positions, Galactic orbital elements, age, and other physical parameters of open star clusters. We show that the population of open clusters is heterogeneous and is divided into two groups differing by their mean parameters, properties, and origin. One group includes the Galactic clusters formed mainly from the interstellar matter of the thin disk with nearly solar metallicities ([F e/H] > −0.2) and having almost circular orbits a short distance away from the Galactic plane, i. e., typical of the field stars of the Galactic thin disk. The second group includes the peculiar clusters formed through the interaction of extragalactic objects (such as high-velocity clouds, globular clusters, or dwarf galaxies) with the interstellar matter of the thin disk, which, as a result, derived abnormally low (for field thindisk stars) metallicities and/or Galactic orbits typical of objects of the older Galactic subsystems. About 70 % of the clusters older than 1 Gyr have been found to be peculiar, suggesting a slower disruption of clusters with noncircular high orbits. Analysis of orbital elements has shown that the bulk of the clusters from both groups were formed within a Galactocentric radius of ≈ 10.5 kpc and closer than ≈ 180 pc from the Galactic plane, but owing to their high initial velocities, the peculiar clusters gradually took up the volumes occupied by the objects of the thick disk, the halo, and even the accreted halo of the Galaxy. Analysis of the relative abundances of magnesium (a representative of the α-elements) in clusters that, according to their kinematical parameters, belong to different Galactic subsystems has shown that all clusters are composed of matter incorporating the interstellar matter of a single protogalactic cloud in different proportions, i. e., reprocessed in genetically related stars of the Galaxy. The [Mg/Fe] ratios for the clusters with thick-disk kinematics are, on average, overestimated, just as for the field stars of the so-called "metalrich wing" of the thick disk. For the clusters with halo kinematics, these ratios exhibit a very large spread, suggesting that they were formed mainly from matter that experienced a history of chemical evolution different from the Galactic one. We point out that a large fraction of the open clusters with thin-disk kinematics have also been formed from matter of an extragalactic nature within the last ≈ 30 Myr. open star clusters, chemical composition, kinematics, Galaxy (Milky Way).

HST trigonometric distances, photometric metallicities, isochronic ages from the second revised version of the Geneva-Copenhagen survey, and uniform spectroscopic F e and M g abundances from our master catalog are used to construct and analyze the age-metallicity and age-relative M g abundance relations for stars of the thin disk. The influences of selection effects are discussed in detail. It is demonstrated that the radial migration of stars does not lead to appreciable distortions in the age dependence of the metallicity. During the first several billion years of the formation of the thin disk, the interstellar material in this disk was, on average, fairly rich in heavy elements ( [F e/H] ≈ −0.2) and poorly mixed. However, the metallicity dispersion continuously decreased with age, from σ [F e/H] ≈ 0.22 to ≈ 0.13. All this time, the mean relative abundance of M g was somewhat higher than the solar value ( [M g/F e] ≈ 0.1). Roughly four to five billion years ago, the mean metallicity began to systematically increase, while retaining the same dispersion; the mean relative M g abundance began to decrease immediately following this. The number of stars in this subsystem increased sharply at the same time. These properties suggest that the star-formation rate was low in the initial stage of formation of the thin disk, but abruptly increased about four to five billion years ago.

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